Sludge dewatering technology of plate and frame filter press

Nowadays, more and more people pay attention to the sludge treatment of plate and frame filter press, and all kinds of sludge dewatering technology, process and equipment are gradually introduced into the design of sewage treatment industry. The sludge dewatering system of plate and frame filter press has been widely used by virtue of its unique advantages of high sludge solid content and low energy consumption. Strengthening the research on the practical application of the sludge dewatering technology of the new plate and frame filter press can promote the normal and stable operation of the sludge dewatering system, improve the operation effect of the system, and provide a valuable reference for the construction of sewage treatment plant.

1. Plate and frame filter press formation and sludge dewatering process. In order to better solve the problem of high organic matter, plate and frame filter press selects the panel type diaphragm extrusion plate and frame filter press structure, and adds the diaphragm extrusion process. In the process of sludge dewatering, the plate and frame filter press mainly realizes dehydration in two ways, that is, it realizes dehydration by press cloth pressure and realizes dehydration by diaphragm extrusion. Pressurized dehydration means that the sludge is fed into the filter press system by the pressure generated by the sludge pump in the feed system, so as to ensure the amount of sludge treated per unit time. Typically, the pressure applied is 5 to 10 kg/cm2. Diaphragm extrusion dehydration means that at the end of pressure dehydration, pressure of 6 ~ 11 kg/cm2 is applied to squeeze the mud cake again to make it more thoroughly dehydrated. Sludge from municipal sewage treatment plants cannot be dehydrated through filtration. For this kind of sludge, the water content of mud cake is reduced by diaphragm extrusion dehydration. Usually, the moisture content of mud cake can be reduced by another 5% ~ 10%.

Sludge dewatering technology innovation and practical application

2.1 Technological innovation of sludge dewatering

2.1.1 Reasonable selection of sludge chemical conditioner Any sewage treatment method must involve sludge dewatering treatment. In other words, solid-liquid separation of sludge must be carried out. There are many kinds of sludge, and the composition of each kind is different. Therefore, the solid particles in the sludge also have different properties. In general, colloidal particles in domestic sewage sludge are extremely small and (negative) charged, which often exist in the form of hydrate, as a colloidal turbid liquid (good stability). It is difficult to concentrate and dehydrate this type of sludge. Based on the characteristics of sludge, several common chemical conditioners are listed and their applications in the new sludge dewatering process are analyzed. At the same time, a large number of productive tests have been carried out on printing and dyeing sewage, domestic sewage and paper sludge sampling. There are three common sludge chemical conditioners:

① Surfactant. Surfactant is a substance which is easily enriched on the surface of solution and can affect the properties of interface. It has fixed hydrophilic and oil-philic base groups, which can be oriented on the surface of solution, thus reducing the surface tension of solution. After the surfactant adsorption, the interface state of the system will change, and then affect the interface properties, which is similar to emulsification, wetting and so on. The surfactant can promote the water in the colloid wall breaking and capillary to get more effective release, can play a good auxiliary role in the separation of colloid solid liquid, condensation. Quaternary ammonium salt surfactants were selected for sludge dewatering in this paper.

② Coagulant. At present, the flocculant of sludge dewatering is widely used in our country as organic flocculant and inorganic flocculant. In this study, inorganic flocculant was mainly used, and an appropriate amount of polymer flocculant was added.

③ coagulant aid. The use of coagulant aid can effectively improve coagulation conditions. In the process of coagulant treatment of wastewater, only using coagulant is often unable to achieve good results, and it is necessary to add coagulant aid.

2.1.2 Improvement of plate and frame filter press for sludge Dewatering The main purpose of technical transformation of plate and frame filter press is to improve the original dewatering pressure and the filtration hydrophobicity of the equipment. In the improvement, we can start from the following two aspects:

① In the improvement of the feeding system, the feeding system of the plate and frame filter press is effectively improved mainly by adding the mud screw distributor, so as to solve the problems of uneven distribution of sludge in the filter plate, uneven thickness of mud cake and different moisture content.

② Improve the filter cloth and filter plate. Through comprehensive and meticulous theoretical calculation, continuous optimization and screening, so that the press cloth can meet the needs of use. Filter plate improvement is specifically the selection of raised particle filter plate, effectively improve the fluidity of sludge in the filter chamber, and improve its uniformity in the filter plate, so as to solve the problem of bursting. The improvement of the press cloth is reflected in the design of conical filter hole weaving, which effectively reduces the resistance of the press cloth medium, and thus enhances the hydrophobic performance of the press cloth.

2.2 Sludge Dewatering Equipment and Practical application According to the relevant requirements of sludge dewatering treatment in the practical application of the resource treatment technology, the sludge pretreatment technology, system integration and sludge dewatering equipment are combined to form a high-efficient combined process and complete sets of equipment and technology.

Take a new modern sewage treatment plant in a city as an example, the designed daily water supply capacity of the plant is 5.0×105 t. The main application of the plant is the conventional enhanced treatment technology, and equipped with relatively complete and advanced sludge treatment equipment, daily production, environmental protection needs are basically met. After applying the new frame sludge dewatering technology in sewage treatment, the sludge production has been reduced by more than 50%. The stacking space of sludge is obviously reduced, the transportation difficulty is greatly reduced, the transportation cost is reduced, and the sludge odor problem has been effectively solved, which lays a good foundation for the sludge follow-up treatment.

3. The application of the sludge dewatering technology of the new plate and frame filter press promotes the automation of the related operations of the diaphragm extrusion plate and frame filter press, and the sealing is better. From feeding to mud cake stripping, the whole process needs no manual operation; Automatic dewatering of mud cake, automatic unloading of filter plate and automatic cleaning of filter cloth have been realized. At the same time, this technology is suitable for water, domestic sewage, paper sewage, printing and dyeing sewage sludge dewatering treatment.